Tetra-n-butylammonium decatungstate supported on Fe3O4 nanoparticles: a novel nanocatalyst for green synthesis of nitroso compounds

Abstract

The aim of this study was to prepare a Fe₃O₄/tetra-n-butylammonium decatungstate (TBADT) catalyst (M-DT) for the selective oxidation of aromatic amine compounds in the presence of hydrogen peroxide (H₂O₂). The material M-DT, prepared from the interactions between TBADT and Fe₃O₄, was fully characterized by Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and, X-ray photoelectron spectroscopy (XPS). The electron transfer between H₂O₂ and TBADT or Fe₃O₄ or M-DT was studied by cyclic voltammetry (CV) using carbon-modified electrodes. The optimized M-DT/H₂O₂ catalytic system can effectively oxidize sulfapyridine (SPD) to nitroso-sulfapyridine (N-SPD) in the pH range of 2.5 to 4.6 with an efficient (93%) and selective conversion (86%). The oxidation rate constant (1.20 × 10⁻² min⁻¹) is much higher with M-DT than with TBADT (2.09 × 10⁻⁴ min⁻¹) or Fe₃O₄ (4.81 × 10⁻⁴ min⁻¹) alone using 5 mM H₂O₂ as a co-catalyst. This M-DT catalyst can be reused 6 times with high efficiency and selectivity.